One of Groupon's major cost centers (along with paying its massive sales force) is user acquisition. And one of the biggest channels for user acquisition is Google. Groupon -- like all of its competitors -- spends a vast sum of money on AdWords.

If Google owned Groupon, Google could simply hardwire Groupon deal results into relevant searches in a separate box, the way it does with YouTube videos, Google News results, and other Google products. This would give Groupon deals a massive leg up over those of its competitors, who would still have to compete with each other for space an AdWords.

There are all sorts of other ways in which Google could help out Groupon's deals, but even if it left the company alone, and did nothing but make that one change, it would create a huge amount of additional value.